Many ways of assembling two metal parts together, such as welding, riveting and screw-fastening, are known.
As regards butt assembling a first planar part at right angles to a second part, the known solutions are not completely satisfactory.
The problem is that riveting or welding requires a fixing portion bent into an L shape to form an edge or tabs, this portion being formed for example at the end of the first part and then extending generally parallel to the plane of the second part, notably to allow rivets to be put in the first case or to provide good mechanical strength in the second.
Preparing such a fixing portion on the first part increases its total manufacturing cost and it will also be observed that these two forms of assembly have the disadvantage of not allowing simple, easy disassembly of the two assembled parts, with the result that, depending on the application, a screw-fastened assembly is preferred.
Document U.S. Pat. No. 5,674,023 discloses a butt assembly of a first planar part with the second part using a generally U-shaped hook or “clip” which holds the two parts at right angles to each other.
The U-shaped assembly hook comprises an intermediate portion connected both to an upper portion, whose free end has a hook arm, and to a lower portion forming a base for fixing the hook.
As can be seen in FIGS. 1 and 2 of that document, the hook arm of the hook is designed to pass through the first part, which for this purpose has a hole while the base portion is fixed to the second part by for example a screw extending through the upper and lower portions.
The end of the threaded rod of the screw used to fix the hook to the second part is received in a complementary tapped hole in the second part and the screw head applies an axial clamping force to the upper portion of the hook so that the hook arm engages with a portion of the first part adjacent to the hole.
When, as illustrated in FIG. 3, the second part is so thin that a tapped hole cannot be made, the threaded rod of the fixing screw passes through the second part and is immobilized by means of a nut.
Such a solution does not however give complete satisfaction, partly because of the mechanical strength of such an assembly when the parts are subjected to severe stresses, such as when constructing a machine frame, and partly because of their cost of manufacture.